AOF question

[Mapleboy]

Hi everyone,
I am building a 2x8 evaporator with AOF/AUF and have a question about the AOF.
Do I need to put air nozzles the whole way around the firebox or can I simply put them along both sides and forget about putting them in the back and front?
Thanks.

[Robert K]

In my application I noticed that the nozzles at the back will constantly flame once the evaporator is up to temp. If you are looking to increase efficiency then you need those nozzles. The idea is to burn the unburnt gasses that remain before they go up the stack. Unless you wish a nice blowtorch effect out the top of the stack, then no nozzles.
Check out the papers posted here on arch design, they are the ones I followed and it works.

[jmayerl]

I went with sides and back. I put in tubes in the front but elected not tap the pipe there because I thought it would help push heat up the stack. So far it has worked very well with only side and rear nozzles and I plan on keeping it that way.

[maple flats]

I went with nozzles all 4 sides, every 6" both sides and back plus one each side of door. My stack temp. has been the lowest ever, I am burning under the pans to use the heat and my boil increased while using less wood. I think you want them both in front and in back too.

[nymapleguy607]

I went a different direction. I have nozzles through the door and across the back wall of the evaporator. The door air and the rear air are on separate controls so you can adjust them how you want.

[derekp]

I'm working on setting up aof as well..it would be nice to see some photos of what configuration you guys used for aof in your fireboxes!!can't seem to find many threads with photos

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[nymapleguy607]

1219712198

Ask and you shall recieve.

[Mapleboy]

Thanks for the help guys!
From the way it sounds I think I definitely need nozzles in the back and sides.

[Sugarmaker]

Some pictures of my unorthodox AOF TRS (Top Rail System).
Basically air nozzles along the sides and the front of the flat pan.
http://i233.photobucket.com/albums/ee170/Sugarmaker/Maple%20related%20pictures/AOF%20TRS%201-19-15/DSC02589.jpg

This is on a 3 x 10 arch.
http://i233.photobucket.com/albums/ee170/Sugarmaker/Maple%20related%20pictures/AOF%20TRS%201-19-15/DSC02590.jpg

Front corner of arch.
http://i233.photobucket.com/albums/ee170/Sugarmaker/Maple%20related%20pictures/AOF%20TRS%201-19-15/DSC02591.jpg

Air inlet and sq air tubes.
http://i233.photobucket.com/albums/ee170/Sugarmaker/Maple%20related%20pictures/AOF%20TRS%201-19-15/DSC02592.jpg

Regards,
Chris

[DocsMapleSyrup]

Nice work on the AOF for the flat pans. I ended up putting 3/8 black pipe nozzles in the tubes for AOF which had a 3/8 ID rather than OD. Is that what you have in stainless? I know the UVM paper on AOF recommends 3/8" nipples but I don't think it specifies ID or OD. Do you know?

[Sugarmaker]

feychad,
Not flat pans (drop flue rear pan). I didn't explain well enough. The nozzles are under the front pan only which is the syrup pan. I think I used about 3/8 O.D. thin wall tubing. So about 1.4 inch hole. Hope that helps.
I think the key to these is putting a control valve in the line so you can regulate the air. Then you can go from a little to a lot as you boil and see what works the best. I know that I have problems with making syrup if I run too much Air Over Fire. So I dial it back, find the sweet spot and mark the valve.
Regards,
Chris

[Paul VT]

Hey sugarmaker! I really like your design! I have AUF now but have been thinking about adding AOF to my rig for a few years but did not want to take brick out and have to drill the side of the arch etc. To much time. What are you using for a air pump?
Thanks
Paul

[derekp]

Figured I would add a few photos of what I settled on after using the info suggested in this thread. It's great having so many people's input on this topic. https://uploads.tapatalk-cdn.com/20160101/b6ab641dff8b7df383ff4632f13acd27.jpghttps://uploads.tapatalk-cdn.com/20160101/e1a7133fde3f1a8f9b3f81542c597180.jpghttps://uploads.tapatalk-cdn.com/20160101/600600aa818819a7f6fe9e209490162b.jpghttps://uploads.tapatalk-cdn.com/20160101/3ca3903032d122efbd442b959a120c5e.jpg

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[derekp]

https://uploads.tapatalk-cdn.com/20160101/a210b3ccde85d3d8a6ea33190037a434.jpghttps://uploads.tapatalk-cdn.com/20160101/6776b5b1204c176288317a62b8e6b778.jpg

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[n8hutch]

Looks great, that's going to be a boiling rig. U might have to tap some more trees:mrgreen:

[maple flats]

sugarmaker, let us know how that works. The original plans I used called for the nozzles to be 6" below the pan, yours may only be 2? ", if that works good it might simplify installs for lots of producers in the future. If it doesn't work as well, you could weld an elbow downward on each and then run the nozzle out at the prescribed angle at 6" for next year. My nozzles were between an inch and 2" out thru the refractory and originally I was going to saw them near flush but then I decided to simply let the extreme heat prune them, after several years the nozzles all still look like new. My thought now is that the air keeps the nozzles cool enough to protect them.

[treehugger]

derekp, have you used your AOF system yet? looks great, I was considering doing something like that. Just trying to figure out a way to do it with out welding. Maybe with steel pipe? please post some results after you have used it with comparison of with and without it, if you have that information. Curious if it will lengthen wood refueling times and improve boiling. Thanks.

[derekp]

I fired up the rig twice with water just to tune up the air system...My first boil wasn't too good and it was obvious that I needed more auf. I ended up changing the auf setup to a single 2" steel pipe with a bunch of holes, and I tied it into the same blower as the aof. Both are on valves to contol the air flow. The line in to aof is 3" and auf is reduced to 2". Once that was fixed, I fired it up again and the difference was incredible. The boil in the front of the flue pan was jumping out of the pan. I have the blower outlet on a switch and when it turned it off to see what would happen, I would lose the intense boil within 10 seconds. The thing I was most impressed with was my stack temp. Last year with just auf my stack temp was 1200 + .... with this system, I could put my hand between the stack and my heat shield...it was actually cold in the sugarhouse which has never happened before. So I ran it for an hour and burned off over 40 gallons of water, and that's including startup and messing around with the air system and running at 1.5" of water...pretty impressed with the whole system. Once I really get going I bet I'll be able to get 50+

[treehugger]

I fired up the rig twice with water just to tune up the air system...My first boil wasn't too good and it was obvious that I needed more auf. I ended up changing the auf setup to a single 2" steel pipe with a bunch of holes, and I tied it into the same blower as the aof. Both are on valves to contol the air flow. The line in to aof is 3" and auf is reduced to 2". Once that was fixed, I fired it up again and the difference was incredible. The boil in the front of the flue pan was jumping out of the pan. I have the blower outlet on a switch and when it turned it off to see what would happen, I would lose the intense boil within 10 seconds. The thing I was most impressed with was my stack temp. Last year with just auf my stack temp was 1200 + .... with this system, I could put my hand between the stack and my heat shield...it was actually cold in the sugarhouse which has never happened before. So I ran it for an hour and burned off over 40 gallons of water, and that's including startup and messing around with the air system and running at 1.5" of water...pretty impressed with the whole system. Once I really get going I bet I'll be able to get 50+

That is impressive for a 2x6.

[treehugger]

Looks like you took the ramp right out of the equation too. Looks pretty steep at the back of the fire box. When I did that to mine the sap would jump out of the front of the flue pan and not get much in the middle or back. I had to give up a little of that back wall to even things out. Good luck this season.

[derekp]

Treehugger,
I was wondering about that...there still is a pretty decent slope...but I was wondering if a bit more would help even out the boil..the front is incredible and there is a full boil throughout, but I was hoping the gysers would carry across more of the pan than just the front..I may throw a small piece of firebrick under the bottom of my wall to create more of a slope and see what happens

[derekp]

Another thing I was wondering..the fire bricks get so hot and hold so much heat, I think it helps the boil, since they are constantly radiating heat under the flues. A lot of people are just using blanket under their flue sections which does not hold heat. I feel like having bricks under the flues may help....anyone have thoughts on this??

[treehugger]

I used blanket on the bottom and brick on the top of it per the manufacturer's recommendation. I also put perlite on the top of that. Its well insulated! When I adjusted the back wall instead of a "straight" up and down, I made it slope up and back to about 18" in the front part of the flue pan and about 1" under the pan. The boil is more uniform for sure.

[DJ Lasell]

1219712198

Ask and you shall recieve.

Hi nymapleguy607,
In the photos you posted on Dec 14, 2015, It looks like your AUF is coming up through the brick in the bottom of your firebox?
Does this design still use grates?
Does it eliminate the need for an ash door?
Thanks DJ

[maple flats]

While I have bricks under my flues, I doubt it would help over blanket. In use the bricks will take on some heat (heat that is costing heat in the flues, and then it will remain essentially constant while you boil and will only add heat when you are shutting down. At that point it is not much help.

[sluggish]

How much air do you guys put into the firebox. As in how many cfm or psi?

[jrthe3]

When I built my arch I made to of the fire box out of 2x4 1/4 in wall square tubing on sides and back and 4x4 1/4 inch wall on front nozzels 3/8 pipe 1/8 inch wall every 4 inch at bottom of tubing so they are 4 inch below pans pointed down Ward at a 15 degree angle it boils amazing kind of shocked myself on how well it works I also have heat exchanger on the back and damper doors to control over and under air